Nutritional powders are well known for use in providing various individuals with sole or supplemental nutritional. These powders are reconstituted with water or other aqueous liquid by the ultimate user to form a nutritional liquid or beverage. These powders most often contain varying amounts and types of protein, carbohydrate, lipid, vitamins and minerals, all depending largely upon the nutritional needs of the intended user.
Nutritional powders often contain a variety of lipids, including unsaturated lipids that tend to be more oxidatively sensitive than some other ingredients. This is especially significant in the formulation of infant nutritional powders since infant formulas typically contain a variety of oxidatively sensitive materials such as unsaturated fatty acids. These fatty acids require additional care during processing to ensure that the unsaturated fatty acids (e.g., linolenic acid, linoleic acid, docosahexaenoic acid, arachidonic acid.) in the finished powder do not excessively degrade by way of oxidation during prolonged storage periods of up to about 36 months, typically from about 24 to about 36 months.
A variety of methods have been used to control oxidative processes in nutritional powders during prolonged storage. Many such methods, of course, are directed to the control of formulation, processing, and packaging conditions that ultimately lead to a more oxidatively stable packaged product. Other methods include the use of a variety of known antioxidants or other stability-promoting ingredients such as ascorbyl palmitate, tocopherols, beta carotene, and even some synthetic materials such as hydroxy anisole (BHA) and butylated hydroxy toluene (BHT) where appropriate.
One such method of providing a more stable nutritional powder is described in U.S. Pat. No. 5,234,702 (Katz et al.) in which a nutritional powder with an oil blend of soy and marine oils is formulated with an antioxidant system made up of ascorbyl palmitate, beta carotene and/or mixed tocopherols, and citrate. This particular method is especially useful in minimizing the undesirable rancidity that often results when unsaturated oils and fatty acids are exposed to the heat and air commonly associated with spray drying processes. The Katz et al. reference teaches that the combination of ingredients provides a highly effective means for improving product stability, even though individual ingredients such as ascorbyl palmitate by themselves were not particularly effective.
It has now been found that lactose-free nutritional powders, including lactose-free infant formulas, are especially susceptible to oxidative processes during prolonged storage, and thus can be more sensitive to vitamin A degradation and the development of rancid oils. Compared to other nutritional powders, these lactose-free powders are often more susceptible to undesirable oxidative processes, and thus represent a sizable challenge for the formulator to produce a stable finished product that will not develop a rancid character during prolonged storage.
It has also been found that these lactose-free nutritional powders, as well as most any nutritional powder containing unsaturated fatty acids and similar other materials, can be formulated into a stable, packaged powder provided that it is formulated with ascorbyl palmitate at a selectively high concentration of at least about 400 ppm, typically from about 400 to about 1000 ppm by weight of the powder. Although ascorbyl palmitate is a known antioxidant for use in various oils, it is also generally known that it is not highly effective when used alone in a nutritional powder.
It has also been found that nutritional powders, especially lactose-free nutritional powders and other oxidatively unstable powders, can also be further stabilized for prolonged storage by the combined use of ascorbyl palmitate at selectively high concentrations as described herein, with at least about 300 ppm of cystine and/or cysteine, by weight of the powder.